While proteasome inhibitors are an effective cancer treatment option, the idea of accelerating the activity of the proteasome for medical purposes represents a novel treatment option for neurological disorders where harmful proteins accumulate and cause disease. Chronic neurological diseases such as Parkinson's, Alzheimer's, Huntington's, Frontotemporal dementia and Spinocerebellar ataxias are characterized by the presence of ubiquitinated protein aggregates and reduced proteasome function. Therefore, while these mutant proteins can be targeted for proteasomal degradation, they are not effectively eliminated by the ubiquitin proteasome system. We recently determined that either genetic or pharmacological inhibition of the ubiquitin hydrolase activity of Usp14 is sufficient to accelerate protein degradation by the proteasome. The levels of several proteins, including tau, TDP-43 and ataxin-3, were significantly decreased following the inhibition of Usp14's ubiquitin- hydrolase activity, indicating that Usp14 can function as an inhibitor of the proteasome. Our working hypothesis is that Usp14 functions to edit the ubiquitin side chains of proteins prior to their commitment to proteasomal degradation, resulting in release of the substrate from the proteasome. The focus of this proposal is to determine if loss of Usp14's ubiquitin hydrolase-activity can reduce the levels of aggregate- prone proteins produced in animal models of Huntington's disease, Frontotemporal dementia and Parkinson's disease. This novel approach to enhancing proteasome function for the clearance of aggregate- prone proteins may lead to a powerful new treatment option for patients suffering from chronic neurological diseases.